Zinc oxide and zinc stannate nanoparticles as well as their composites due to their attractive electrical and optical parameters are promising candidates for a wide range of application in solar cells, sensors, photocatalysis for the degradation of organic pollutants. The aim of the present work was to prepare particulate nanocomposites with different content of the components in the ZnO-Zn2SnO4/Ag system by using microwave synthesis and to compare their photocatalytic activity in degradation of methylene blue solution. ZnO-Zn2SnO4/Ag system nanoparticles were prepared by heating mixtures of the salt solutions in microwave reactor (Masterwave BTR, Anton Paar) at 160–180 oC. The specific surface area of the prepared nanocomposites was in the range of 19–28 m2/g in the dependence on the phase composition. Crystallite size of the oxides and Ag particles was in the range of 30–60 nm and 30–70 nm, respectively. The powders were composed of tetra-pod shaped or rod-like particles of ZnO and cubic particles of Zn2SnO4. The silver particles were situated on the surface of oxides. The photocatalytic activity depended on ratio of the components, content and crystallite size of Ag. The highest photoactivity showed ZnO/Ag, ZnO-Zn2SnO4/Ag.